1. Field of the Invention
The present invention relates to an optical fiber attenuator, and more particularly an apparatus for inducing a controllable and consistent light loss or attenuation in a fiber optic cable.
2. Background Information
The present invention is directed to an optical fiber attenuator, which permits variation of the bend radius of a fiber optic cable, thereby inducing a controllable and consistent light loss or attenuation in the fiber optic cable. More particularly, the optical fiber variable attenuator varies the light loss in a fiber optic cable by varying the bend radius of the fiber optic cable which is wrapped around a mechanical spring clip.
The broad general concept of modifying the attenuation of a fiber optic cable by wrapping the fiber optic cable around a diameter and changing the radius of curvature of the wrapped fiber optic cable is generally well known. Bending fiber optic cable causes light loss in the cladding of the fiber optic cable and is employed in industries which utilize fiber optics. For example, the optical fiber variable attenuator may find application in the broad band cable television field.
Recent developments in a Transimpedence Amplifier (TIA) Return Path Receiver have brought about a number of performance and cost enhancements. However, these improved TIA Return Path Receivers do not operate at optical levels much greater than 0 dbm. Conventional optical fiber attenuators operate in an attenuation range which is outside of the optimal attenuation range of the improved TIA Return Path Receiver. In addition, conventional optical fiber attenuators are relatively complicated and relatively expensive to manufacture. An economic means to provide light at optimal attenuation ranges for the improved TIA Return Path Receivers is needed that will permit an overall gain reduction without degrading noise figures or return losses.
The present invention provides an optical fiber attenuator that is relatively inexpensive and permits easy adjustment of the attenuation. More particularly, the optical fiber attenuator of the present invention provides an adjustable spring clip in a housing. The fiber optic cable is wrapped around the spring clip in one or more loops. Adjusting the position of the spring clip modifies the radius of curvature of the loops and hence modifies the attenuation of the fiber optic cable.
Briefly stated, the present invention comprises an optical fiber attenuator for adjusting the attenuation of a fiber optic cable. The optical fiber attenuator is comprised of a channel housing having a generally L-shaped cross section with a first leg and a base extending therefrom. A spring clip having a first end and a second end is positioned within the channel housing. The first end of the spring clip is secured to the channel housing while the second end of the spring clip is adjustably positioned to move between a first position adjacent the second leg of the channel housing and a second position adjacent the first end of the spring clip. A fiber optic cable can be wrapped around the spring clip such that as the second end of the spring clip is moved between the first and second positions, the attenuation of the fiber optic cable is modified by changing a radius of curvature of the fiber optic cable.
In another aspect, the present invention is a combination fiber optic cable and optical fiber attenuator for adjusting an attenuation of the fiber optic cable. The combination comprises a channel housing which is generally L-shaped in cross section. The channel housing includes a first leg and a base extending therefrom. A spring clip is positioned within the channel housing. The spring clip has a first end and a second end. The first end is secured to the first leg. The second end is adjustably positioned to move between a first position adjacent the second leg and a second position adjacent the first end of the clip. A fiber optic cable is wrapped around the spring clip such that as the second end of the spring clip is moved between the first and second positions the attenuation of the fiber optic cable is modified by changing a radius of curvature of the fiber optic cable.